(function($) {
	$.fn.ajaxfileupload = function(options) {
		var settings = {
			params: {},
			action: '',
			onStart: function() {},
			onComplete: function(response) {},
			onCancel: function() {},
			validate_extensions: true,
			valid_extensions: ['gif', 'png', 'jpg', 'jpeg'],
			submit_button: null
		};

		var uploading_file = false;

		if(options) {
			$.extend(settings, options);
		}

		// 'this' is a jQuery collection of one or more (hopefully) 
		//  file elements, but doesn't check for this yet
		return this.each(function() {
			var $element = $(this);

			// Skip elements that are already setup. May replace this 
			//  with uninit() later, to allow updating that settings
			if($element.data('ajaxUploader-setup') === true) return;

			$element.change(function() {
				// since a new image was selected, reset the marker
				uploading_file = false;

				// only update the file from here if we haven't assigned a submit button
				if(settings.submit_button == null) {
					upload_file();
				}
			});

			if(settings.submit_button == null) {
				// do nothing
			} else {
				settings.submit_button.click(function(e) {
					// Prevent non-AJAXy submit
					e.preventDefault();

					// only attempt to upload file if we're not uploading
					if(!uploading_file) {
						upload_file();
					}
				});
			}

			var upload_file = function() {
				if($element.val() == '') return settings.onCancel.apply($element, [settings.params]);

				// make sure extension is valid
				var ext = $element.val().split('.').pop().toLowerCase();
				if(true === settings.validate_extensions && $.inArray(ext, settings.valid_extensions) == -1) {
					// Pass back to the user
					settings.onComplete.apply($element, [{
						status: false,
						message: 'The select file type is invalid. File must be ' + settings.valid_extensions.join(', ') + '.'
					}, settings.params]);
				} else {
					uploading_file = true;

					// Creates the form, extra inputs and iframe used to 
					//  submit / upload the file
					wrapElement($element);

					// Call user-supplied (or default) onStart(), setting
					//  it's this context to the file DOM element
					var ret = settings.onStart.apply($element, [settings.params]);

					// let onStart have the option to cancel the upload
					if(ret !== false) {
						$element.parent('form').submit(function(e) {
							e.stopPropagation();
						}).submit();
					} else {
						uploading_file = false;
					}
				}
			};

			// Mark this element as setup
			$element.data('ajaxUploader-setup', true);

			/*
			// Internal handler that tries to parse the response 
			//  and clean up after ourselves. 
			*/
			var handleResponse = function(loadedFrame, element) {
				var response, responseStr = $(loadedFrame).contents().text();
				try {
					//response = $.parseJSON($.trim(responseStr));
					response = JSON.parse(responseStr);
				} catch(e) {
					try {
						response = $.parseJSON($.trim(responseStr))
					} catch(e) {
						response = responseStr;
					}
				}

				// Tear-down the wrapper form
				element.siblings().remove();
				element.unwrap();

				uploading_file = false;

				// Pass back to the user
				settings.onComplete.apply(element, [response, settings.params]);
			};

			/*
			// Wraps element in a <form> tag, and inserts hidden inputs for each
			//  key:value pair in settings.params so they can be sent along with
			//  the upload. Then, creates an iframe that the whole thing is 
			//  uploaded through. 
			*/
			var wrapElement = function(element) {
				// Create an iframe to submit through, using a semi-unique ID
				var frame_id = 'ajaxUploader-iframe-' + Math.round(new Date().getTime() / 1000)
				$('body').after('<iframe width="0" height="0" style="display:none;" name="' + frame_id + '" id="' + frame_id + '"/>');
				$('#' + frame_id).get(0).onload = function() {
					handleResponse(this, element);
				};

				// Wrap it in a form
				element.wrap(function() {
						return '<form action="' + settings.action + '" method="POST" enctype="multipart/form-data" target="' + frame_id + '" />'
					})
					// Insert <input type='hidden'>'s for each param
					.before(function() {
						var key, html = '';
						for(key in settings.params) {
							var paramVal = settings.params[key];
							if(typeof paramVal === 'function') {
								paramVal = paramVal();
							}
							html += '<input type="hidden" name="' + key + '" value="' + paramVal + '" />';
						}
						return html;
					});
			}
		});
	}
})(jQuery)